Classification of Vitamins
Classically, vitamins have been divided into two groups based on their solubilities in fat solvents or in water.
Thus, fat-soluble vitamins include A, D, E and K, while vitamin of the B-complex and C are classified water soluble.
Fat soluble vitamins are found in foodstuffs in association with lipids.
The fat soluble vitamins are absorbed along with dietary fats, apparently by mechanisms similar to those involve in fat absorption.
Conditions favorable to fat absorption, such as adequate bile flow and good micelle formation, also favor absorption of the fat-soluble vitamins.
Water soluble vitamins are not associated with fats, and alterations in fat absorption do not affect their absorption.
Three of the four fat-soluble vitamins (vitamins A, D and E) are well stored in appreciable amounts in the animal body. Except for vitamin B12, water soluble vitamins are not well stored, and excesses are rapidly excreted.
A continual dietary supply of the water soluble vitamins and vitamin K is needed to avoid deficiencies.
Fat-soluble vitamins are excreted primarily in the feces via the bile, whereas water soluble vitamins are excreted mainly in the urine.
Classification of Vitamins
